We need to find the word that does not belong to the group based on a common characteristic. (1) Copper is a chemical element (metal). (2) Tin is a chemical element (metal). (3) Platinum is a chemical element (metal). (4) Brass is an alloy, specifically a mixture of copper and zinc. Copper, Tin, and Platinum are all pure metallic elements. Brass is an alloy (a mixture of metals). Therefore, Brass is the word that is not like the others. This matches option (4).